Pulse width modulation (PWM) is used in some communications applications. PWM signals, which are also referred to as PWM sequences, may originate from analog signals that have been sampled or by other signals that have been quantized. In some applications, delta-sigma modulation (DSM) is applied to the quantized signals. In DSM, a voltage level is generated during a specific sampling period, wherein the voltage level is representative of the value of the voltage during the sampling period.
The generation of PWM sequences from DSM signals is a nonlinear process, which results in nonlinear distortions such as noise folding. The nonlinear distortions limit the inband signal to noise ratio and the out of band adjacent channel power ratio performance. Further noise is introduced into the PWM sequences if these signals are mixed with a carrier signal. Therefore, the PWM sequences are limited in many communications applications.